Most users of online dating sites fib about age, height and weight

When it comes to online dating, netizens fib about their age, height and income, revealed a survey.

Social scientists who have studied data collected by matchmaking sites in recent years found that women hit their dating prime at only 21; short, poor men might as well delete their Match.com accounts; and half of cyberdaters are lying about their weight.

And they have concluded that people are way harsher online than they are in real life.

For every inch a man is under 5-foot-10, he should make $35,000 to $40,000 more a year to be seen as equally "attractive" as his taller counterpart, says Dan Ariely, author of The Upside of Irrationality.

With the help of an unnamed popular dating site, Ariely polled 28,000 online daters to reach that disturbing conclusion.

Women are more likely to rate men as "below average looking."

Men often choose a mate based on body mass index and age. But the sexes have one thing in common -- they both lie.

Men are on average 2 inches shorter than they say in their profiles, while women are an inch shorter. About 50% of daters fib about their weight.

Almost everyone exaggerates their income by 20%, according to trends tracked by online dating service OKCupid and shared with The Post.

Racial preferences vary by race and gender, according to Ariely's research.

According to the research, 40% of African-American females dated only within their own race, while only 5% of African-American men did the same.

Twenty-eight percent of white women— as opposed to 15% of white men— dated only within their race.

"The only race that we didn't find any preference was Chinese women. Close to zero had no preference on race, which undeniably creates dating trouble for Chinese men," the New York Post quoted Ariely as saying.

Men are more hung up on youth.

According to men, women hit their "attractiveness peak" at 21.

When it comes to women, men are sexiest at 27, according to OKCupid.

Men become more attractive the more education they have -- but women receive no benefit from any degree beyond a bachelor's, said Ariely.

Ariely also proved that women do in fact love a man in uniform. The sexiest male job or a man if salary was taken out of the equation — police officer or firefighter.

Oddly, smoking increases a woman's online popularity, said Ariely.

"I think it's because it correlates with promiscuity. They think women who smoke go to bars, care less about their health, are more adventurous. And don't get me started on the oral issue," said Ariely.